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Sana,
Can you please post the output from following commands:
1- lspv
2- lsvg -p <VGNAME> Example: lsvg -p backupvg
Take a note of physical volume names (eg. hdisk18 and hdisk9) Then run these commands:
3- lspv -l <PV name> For example: lspv -l hdisk18
Then run the same command with other PV, example: lspv -l hdisk19 or whatever the name of the PV is.

So the VG in question (backupvg) is on hdisk18 and hdisk22
By the way you have a typo in your command. You are typing "hdsik18" and of course AIX does not find this as a device. Also you are typing "hdsik22" which should be "hdisk22"
So please correct the typos and send the output back again